An EL display apparatus can be classified into two types including active matrix type and passive matrix type by its driving method. The active matrix EL display apparatus is driven by a current and each matrix array pixel region thereof includes at least one thin film transistor (TFT) serving as a switching device. The thin film transistor adjusts a driving current based on a change in storage potential of a capacitor in order to control luminance and gradation of the pixel region.
Among the active matrix EL display apparatuses, an active matrix organic EL display apparatus includes, as fundamental constituent elements, an electrode layer, an organic emission layer which is formed on the electrode layer and is made of an organic EL material, and another electrode layer formed on the organic emission layer. In a case of a bottom emission type display apparatus in which light is emitted to a substrate side, a substrate and a lower electrode layer are required to be light transmissive, and thus a transparent electrode is used as the lower electrode layer. A conductive oxide material is normally used for the transparent electrode, and in some cases, a surface of the conductive oxide is contaminated by an organic substance. In such case described above, it is difficult to inject a current to the organic emission layer.
Therefore, as disclosed in US Patent Application Publication No. 2005/082515, it is necessary to perform, as a hydrophilic process, ultraviolet irradiation and surface cleaning with ozone generated by the ultraviolet irradiation immediately before the formation of the organic emission layer of the organic EL display apparatus on the transparent electrode layer, thereby removing organic contaminants from the surface of the transparent electrode.
However, when the above-mentioned method is performed as a method of cleaning the surface of the transparent electrode, there is a problem that an ultraviolet irradiation process is further required. In addition, there is another problem that a process of providing a light shielding layer is further required in order to prevent a phenomenon in which, when the thin film transistor of the matrix array pixel region is irradiated with ultraviolet light, the thin film transistor degrades, and thus does not serve as the switching device. In particular, when a channel layer of the TFT is made of an oxide semiconductor containing In, Ga, Zn, or the like, there is a case where a characteristic of the TFT significantly changes depending on an ultraviolet irradiation condition.